The present invention relates generally to a cooling arrangement.
More particularly, the invention relates to a cooling arrangement for rolled materials, such as wires, rods and the like.
On completion of the final rolling step these materials, especially wire, must be superficially cooled rapidly and repeatedly; such superficially cooling must be as uniform and intensive as possible over the entire surface area of the workpiece. Moreover, to obtain the desired effect it is necessary--as explained e.g., in U.S. Pat. No. 1,211,277--to remove the cooling fluid quickly after each superficially cooling step so that the heat at the core of the workpiece can quickly raise the temperature of the workpiece surface again.
To effect such superficially cooling it is known to use tubes through which the workpiece, such as wire, travels to be contacted in one tube section with a cooling fluid (e.g., water) which is rapidly withdrawn at another tube section. It is also known to arrange several such tubes one behind the other, to provide an installation in which the wire can be repeatedly superficially cooled and allowed to reheat (due to its core heat) in intermediate stations.
One problem with this known state of the art is that it is not well suited for the production of special high-quality wires, for example wires in which a core with fine-lamellar perlite and with an outer martensite layer of a specific thickness is to be produced. The known arrangements permit a rapid application of the cooling medium to the wire surface, but do not permit a rapid enough subsequent withdrawal of the cooling medium out of contact with the surface. This, however, is a major requirement when it is desired to produce certain steels of uniform high quality, since to obtain these it is necessary to subject the workpiece to rapid superficially cooling (to produce a maximum temperature difference between the workpiece core and the workpiece surface) and thereafter to assure equally rapid temperature equalization between the core and the workpiece surface due to reheating of the surface by the heat of the core.
In the known cooling arrangements the length of the path portion in which the workpiece is first contacted with cooling fluid is quite substantial; this means--especially if the workpiece coming froom the final rolls of the mill travels at a high rate per unit time--that the length of the path portion in which the cooling fluid is subsequently conducted away from the workpiece must also be very long, since otherwise it is impossible to remove all the cooling fluid. Because of this, the known arrangements are not suitable under the special circumstances outlined above, since the duration of contact between the cooling medium and the workpiece is too long to permit the necessary rapid superficially cooling and equally rapid reheating (due to the core heat) of the workpiece surface.
Moreover, the known arrangements do not permit contacting of the workpiece over a substantial length with an adequate quantity of cooling fluid, since large portions of the path travelled by the workpiece are shielded by long workpiece guiding tubes which prevent access of the cooling fluid to the workpiece. Hence, only small and inadequate quantities of cooling fluid can be sprayed onto the workpiece through a nozzle at one end of the respective guide tube--and the thus admitted fluid can moreover be removed only through a few small openings at the other end of the guide tube. Since these bores create a flow resistance for the cooling fluid, they increase the dwell time of the fluid (i.e., the time for which it remains in contact with the workpiece surface). Thus, neither the initial chilling nor the subsequent reheating of the workpiece can take place fast enough to meet the requirements which are made when steel of uniform high quality is to be produced.
Finally, the known arrangements have still a further disadvantage, in that the ends of workpieces (especially wires) travelling through the guide tubes tend to become caught in the bores or slots provided in the guide tubes for evacuation of the cooling fluid. This leads inevitably to malfunctions and consequently to uneconomical machine down-time.
Another prior art arrangement is known from German Pat. DE=PS No. 557,455. Here, the workpieces are guided through a housing which is provided with several annular water-stripping elements. Because of the guidance of the workpieces these elements must be arranged in close succession so that the cooling water can be sprayed only onto short increments of the workpiece surface. Sudden superficially cooling of the workpiece surface over a substantial length of the same is not possible, nor can a uniform superficial cooling of the work surface be obtained by the disclosed spraying action. This arrangement is, therefore, suited for its own specific purpose but not for treating workpieces of the type outlined above, especially since immediately downstream of each of the stripping elements another cooling step takes place so that due to the close spacing of these elements, the requisite reheating of the workpiece from the core heat cannot occur.
In another cooling arrangement which has been proposed for cooling rolled stock including wires, rods and the like, a first end member and a second end member are provided which are longitudinally spaced from one another and which have respective axially aligned passages, a plurality of rods connecting the end members and angularly spaced about the axis of alignment of the passage, the rods having first ends connected to the first end member on a first circle surrounding the passage of the first end member and also having second ends connected to the second end member on a smaller-diameter second circle surrounding the passage of the second end member, so that the space bounded by the bars converges from the first towards the second end member. Means are provided for admitting cooling fluid into contact with a workpiece travelling through the passages, so that the cooling fluid can escape between the bars subsequent to such contact.
This arrangement is highly advantageous, because it permits a rapid outflow of the cooling medium away from the just-contacted workpiece, due to the large interstices between the bars and also due to the circular bar cross-section which offers minimum flow resistance.
It has also been proposed to surround that end region of the bars at which the cooling medium is adjusted with a sleeve or jacket which is concentric to the longitudinal axis of the passage through which the workpiece advances. The cooling medium is to be admitted into this jacket and to flow from there between the bars into contact with the workpiece, whereupon it flows out again between the bars at a location further downstream.
However, in certain applications even this otherwise highly advantageous arrangement still does not offer the desired optimum control over the pressure conditions during contacting of the cooling medium with the workpiece surface.